1. Field of the Invention
This invention relates generally to radio wave communications antennas, and more specifically to a flat reflector antenna for satellite signal reception as well as local radio and television reception.
2. Description of Related Art
Typical direct broadcast satellite (DBS) reception systems currently employ parabolic dish antennas that are both bulky and not aesthetically pleasing. Furthermore, these systems are not able to receive radio and TV signals of local origin. In order to improve the aesthetic character of satellite antenna systems, low profile or "flat-dishes" have been developed, however, previous low profile DBS antennas have been deficient in important RF performance parameters such as for example, gain, low sidelobes, high cross-polarization isolation, and also in necessary mechanical features such as structural integrity and light weight. These devices, due to their complexity, have not been able to be produced at the low cost required for broad commercial success.
As an example of the foregoing, attempts continue in the development of a low profile, high gain flat antenna to achieve acceptable satellite TV signals. Various flat antenna designs using printed circuit, Fresnel zone reflectors and phased array antenna technologies have been tried. Printed circuit flat antennas are limited in bandwidth, aperture efficiency, cross polarization isolation and have high manufacturing cost. Flat phased array antenna designs exhibit very low aperture efficiency, typically in the range of approximately 30-37% versus a high of 70% for an off-set parabolic dish antenna. This type of antenna design also exhibits very poor cross-polarization isolation and high production costs. Fresnel zone plate antennas, which are essentially flat, have not been able to adequately meet all the previously mentioned antenna parameters. The most important limitations of these antennas are primarily related to the above mentioned loss of performance and poor gain.
A flat antenna is disclosed in C100: Tsiger Planar Antenna a technical description from Tsiger Planar Inc. of Colorado Springs, Colorado. This device is 65 inches square by only 2.5 inches in thickness, and weighs 65 pounds. It is a combination Fresnel lens and zone plate of a design not yet disclosed nor having patents issued. Further, of interest in the matter of flat antennae is an article entitled, The New Age of Earth Station Technology published in Via Satellite, May 1994. No prior art has been found which discloses a combination of multi-stepped reflectors, axis fed, lens corrected splashplate feed with VHF/UHF antenna combined elements for the simultaneous reception of satellite and local station off-air broadcast signal reception of high quality.
The present invention fulfills these needs and provides further related advantages as described in the following summary.